Constant tension chain jack assembly



March 10, 1970 E. E. HORTON:

' CONSTANT Y'IENHSION cnAIn JAcx ASSEMBLY Filed March 19. 1968 2 Sheets-Sheet 1 INVENTOI? EDWARD 6'. H01? TON United States Patent 3,499,629 CONSTANT TENSION CHAIN JACK ASSEMBLY Edward E. Horton, Portuguese Bend, Calif., assignor to Ocean Science and Engineering, Inc., Washington, D.C., a corporation of Delaware Filed Mar. 19, 1968, Ser. No. 714,289 Int. Cl. B66f 3/24; F15b 1/04 US. Cl. 254-93 Claims ABSTRACT OF THE DISCLOSURE An apparatus for the step-by-step paying-out and hauling-in of a chain from a floating vessel wherein hydraulic cylinder means having a gas accumulator bias means working with the expansion chambers thereof permits limited movement of the chain for relieving tension and absorbing shock caused by vessel movements.

This invention relates generally to an apparatus for raising and lowering heavy submerged weights from the bottom of the sea by a chain jacking assembly mounted on a floating vessel. More specifically the invention relates to an apparatus which retrieves sunken objects with a chain and includes means for paying out and hauling in the chain while compensating for the rolls and heaves or other motions of the ship. The device is one particularly adapted for the retrieval of sunken vessels, the raising and lowering of heavy anchors, the pulling down of platforms or buoys and other requirements where heavy objects are manipulated from a floating ship. In addition, the invention is particularly well suited for raising and lowering drilling platforms whereby the sub-base can be lowered to the sea floor from a floating barge or other suitable vessel.

A principal objective of this invention is to provide a chain jacking assembly for lowering and raising the chain in a positive step-bystep procedure.

Another important object of the invention is to provide a means to compensate for vertical movement of the ship during the raising and lowering operations.

Another object of the invention is to maintain constant tension on the lifting chain by having hydropneumatic means compensating for the rolls and heaves of the floating vessel.

Another important objective of this invention is to provide a means for equally distributing the weight of the object which is to be raised or lowered over a number of chains. This is accomplished by the hydropneumatic accumulator system which can be adjusted such that all chain systems are operated at predetermined tensions.

Another important objective of this invention is to provide a hydropneumatic accumulator system wherein the stresses caused by the ship movements are substantially isolated from the lifting chain.

A still further objective of this invention is to provide an adjustable gas spring accumulator for developing a very low spring constant whereby the frequency of the spring response can be adjusted to a point much lower than the rolling frequency of the ship-to thereby isolate the ship motion from the object retrieval chain.

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawings, wherein:

FIGURE 1 is a schematic, diagrammatic view of the system;

FIGURE 2 is a partial enlarged diagrammatic elevation view of a portion of the system shown in FIG- URE 1; ..1 1.

3,499,629 Patented Mar. 10, 1970 "ice FIGURE 3 is an enlarged view of the chain stopper mechanism; and

FIGURE 4 is a view of the chain stopper pawls with actuators.

Referring now to the drawings wherein like elements indicate like parts, the numeral 10 generally indicates the chain jack assembly of this invention. The assembly is secured to the deck of a ship indicated by the numeral 8 12. Also housed on the deck is a chain supply locker 14 in which a length of chain 16 is stored. The chain 16 is led from the chain supply locker over a sheave 18 through the assembly 10 and then outwardly to a sheave 19. The outward sheave 19 is supported at the side of the vessel or is extended outwardly from the vessel by a boom construction not shown. From the outward sheave 19, the chain extends downwardly to the object to be lifted.

Two separate but cooperating power means are provided for paying out and hauling in chain 16. A hydraulic assembly indicated generally by the numeral 20 is the primary means for these purposes. With reference to FIG- URE 1, it can be seen that a wildcat drive motor 22 is also provided to haul in or pay out the chain from its locker in those instances where relatively light or no loads are present. Additionally, as will be seen hereinafter, the wildcat maintains the chain taut during operation of the means 20. The wildcat drive is powered through a slip clutch 24 and to sheave 18 by way of a drive shaft 26. The drive shaft and sheave 18 are supported on the deck 12 via a trunnion assembly 28.

The principal elements of the primary power means 20 are a pair of hydraulic cylinders 30 and 32. Slidably received in these cylinders is a first pair of pistons 34 and 36 having piston arms 38 and 40 extending forwardly and having their outer ends interconnected by a bracket 42. The bracket 42 carries a chain stopper apparatus 44 which is best seen in FIGURES 2 and 3. The chain stopper 44 includes a pair of pawls 46 and 48 which engage the chain 16 as it passes therethrough. As seen in FIGURE 2, the pawls will restrict movement (pay-out direction) of the chain to the left but will permit the chain to freely pass to the right (haul-in direction).

The pistons 34 and 36 respectively divide the hydraulic cylinders 30 and 32 into expansion chambers 54 and 56 and middle chambers 50 and 52. A second set of pistons 64 and 66 are slidably received in cylinders 30 and 32 longitudinally rearwardly of the pistons 34 and 36. The pistons 64 and 66 are slidable between the middle chambers 50 and 52 and rearward chambers 68 and 70. EX- tending rearwardly from the pistons 64 and 66 are a pair of piston arms 72 and 74 joined at their outer ends by a bracket 76. The bracket member 76 carries a second chain stopper device 80 having pawls 86 and 88 restrict pay-out movement of chain 16 but permit the haul-in movement thereof. In other words, they are operational in the same manner as the pawls of chain stopper 44.

The pistons 34 and 36 are sealed at either end by mem- A bers 90.

The main motivating force of the hydraulic cylinder means 30 and 32 is a variable volume, reversible hydraulic pump having an output line 102. The output line 102 is communicated with the middle expansion chambers 50 and 52 by a pair of hydraulic lines 104' and 106. Disposed across line 102 is a solenoid control valve 108. The valve 108 is of a type which causes a selected amount of fluid to enter or leave chambers 50 and 52 upon each actuation thereof.

The main load of any outward pull on chain 16 is principally supported by the fluid in chambers 54 and 56. An accumulator 110, divided'into anair chamber 112 and a hydraulic chamber 114 by a sliding piston member 116;

3 has its hydraulic chamber 114 communicated with the forward chambers 54 and 56 via conduits 118 and 120.

The gas chamber 112 is maintained at a selected gas bias pressure by a plurality of pneumatic storage back-up accumulators 122, 124 and 126 via the air pressure hose line 128. Disposed between the gas chamber 112 and the the back-up accumulators is a conventional pressure regulator control 130. Additional gas storage members 132 and -134 are connected to hose line 128 between the pressure regulator 130 and the chamber 112. The additional gas storage members are under the separate control of individual pressure regulators 136 and 138.

As will be seen more clearly hereinafter, the accumulators provide a gas spring with a very low spring constant. Because of the very high volume ratio between the chamber 112 and the accumulators, the gas spring response can be adjusted to a very slow frequency. This permits the user to tune the response of the gasspring to a frequency much lower than that of the ship itself. Thus, energy is not transferred upon every roll of the ship. An accumulator system partially shown at 110 is provided for the spring bias in chambers 68 and 70. In this system, elements corresponding to the elements of the previously described accumulator system are indicated by the same numerals with the addition of prime marks.

In operation, chain 16 is first extended over the sheave 18 through the chain stopper devices 80 and 44 and from there over forward sheave 19 which is normally disposed over the load to be lifted or lowered. The end of chain 16 is adapted to be affixed to a load of substantial weight. In order to lift this weight, the chambers 50 and 52 are pressurized by pump 100. As the chambers 50 and 52 expand, the pistons are moved outwardly toward their re spective ends. Since pawls 86 and 88 are in gripping en gagement, the chain 16 is drawn inboard (to the right in the drawings). During this movement, the pawls 46 and 48 are riding over the chain. At the end of this expansion stroke, the stroke distance being controlled by the volumetric characteristics of valve 108, the pump 100 is reversed and fluid is removed from chambers 50 and 52 causing these chambers to contract. During this portion of the stroke, the pawls of stopper 44 are in engagement with chain 16 and thus carry the chain to the right while the pawls of stopper 80 are riding over the chain. When the pistons reach their neutral position, the pump is again reversed and the cycle is repeated. The wildcat drive maintains a minimum tension on the chain during the entire cycle.

With the pawl arrangements as described above, the apparatus is particularly useful for the hauling in of heavy loads. The pawl placement of FIGURE 3 does not permit pay-out movement of the chain. Of course, it is simple enough to manually move the pawls out of engagement when the chain is not under load to permit pay out.

However, there are circumstances when it is necessary to lower a heavy object. The unit can be connected for such use by merely extracting the pins 150 from apertures 152 and displacing the pins and their respective pawls to the positions shown in FIGURE 3. Stop bosses 154 are provided on the interior surface of stoppers 44 and 80 to position the pawls in their engagement positions.

In FIGURE 3 the chain stopper mechanisms 44 and '80 are shown in enlarged detail showing a further embodiment of the invention. In this embodiment the pawl units 46, 48, 86 and 88 are connected respectively to hydraulic actuators 140, 142, 143 and 144. The actuators are utilized to move the pawls independently of the particular forces to which the pawls are subjected by chain tension. Thus, the lifting and lowering capacities described above can be accomplished without a requirement of removing pins or otherwise changing the pawl pivot positions.

For instance, when lowering a weight, the pump 100 pressurizes chambers 50 and 52 to extend the arms 38, 40, 72 and 74. During this expansion stroke, the arms of the actuators 142 and 143 are Withdrawn so that pawls 86 and '88 are disengaged and the pawls 46 and 48 are moved to engagement with the chain to carry the chain inboard. When pump is reversed to withdraw fluid from chambers 50 and 52, the pawls are moved to their opposite position. The pawls are similarly controlled for lifting a weight.

There has been described an apparatus which can haul in, pay out or hold fast a loaded chain extending from a vessel while maintaining constant tension on the chain While performing any of these functions. For instance, presume the apparatus in neither paying out nor hauling in and the deck 12 heaves upwardly away from the load to which the chain is attached. The stopper units will not permit movement in this direction but all of the pistons 34, 36, 64 and 66 will move to the left permitting a relaxing pay out of the cable. Since the volumes in chambers 50 and 52 are fixed (when pump 100 is neither supplying nor extracting) the movement is against the spring bias in chamber 112. There is a consequent reduction in pressure in pneumatic chamber 111 of accumulator 110. The accumulators will then work to stabilize the system until the equilibrium position of FIGURE 1 is realized.

As the deck 12 dips toward the load, the opposite occurs. That is, the equilibrium pressure will be upset and the pistons will move to the right in opposition to the pneumatic bias created in chamber 111. Again the gas bias systems will act until the equilibrium position is realized. Since the solenoid valve 108 meters a particular amount of fluid during the expansion and contracting stroke of a lifting or lowering operation, the accumulator balance system is just as effective during these operations.

In a general manner, while there has been disclosed effective and efiicient embodiments of the invention, it should be well understood that the invention is not limited to such embodiments, as there might be changes made in the arrangement, disposition, and form of the parts Without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

What is claimed is:

1. An assembly for raising, lowering and suspending a heavy object by a chain from a floating vessel disposed over said object, the improvement for maintaining said chain under substantially uniform tension comprising a hydraulic cylinder means afiixed to the deck of said vessel along an intermediate length of said chain, a piston means slidable within said cylinder means and dividing said cylinder means into first and second chambers, chain engaging means connected to said piston means, a first hydropneumatic spring means in communication with said first chamber, a second hydropneumatic spring means in communication with said second chamber, an accumulator means forming a part of said first hydropneumatic spring means and means for adjusting the volumetric ratio between said first chamber and said accumulator means.

2. The improvement of claim 1 wherein said first and second hydropneumatic spring means exert pressures on said piston means to normally center said piston means longitudinally of said cylinder means.

3. The improvement of claim 1 wherein said piston means comprises first and second members having a middle chamber therebetween.

1 4. The improvement of claim 3 wherein a variable power reversible pump delivers fluid and extracts fluid from said middle chamber.

5. The improvement of claim 4 wherein said first piston member has an arm extending outwardly from first chamber end of said cylinder means and said second piston member has an arm extending outwardly from the second chamber end of said cylinder means and said chain engaging means comprised of one-way pawl means are mounted on each of said arms in engagement with said chain.

6. The improvement of claim 5 wherein said pawl means restrict movement of said chain toward said object but permit said chain to freely pass in the opposing direction.

7. The improvement of claim 5 wherein actuators for selectively positioning said pawls are mounted on said assembly.

8. The invention of claim 2 wherein said cylinder means includes first and second cylinders and said first piston means includes first and second piston arms extending beyond the end of said cylinders andsaid chain engaging means comprised of cooperating pawls are mounted at their outer ends in engagement with said chain.

9. The invention of claim 8 wherein said second piston means includes third and fourth piston arms extending beyond the outer ends of said cylinders and second co- 10. The invention ofclai-m 1 wherein a drive motor having a slip clutch is disposed on said deck in driving relationship with said chain.

References Cited UNITED STATES PATENTS 3,163,005 12/1964 Reed 60-51 3,361,035 1/1968 Rountree 91152 10 OTHELL M. SIMPSON, Primary Examiner DAVID R. MELTON, Assistant Examiner US. Cl. X.R.

operating pawls are pivotally secured to the outer ends 15 6051 thereof. 

